In recent years, imaging apparatuses are in wide use which perform imaging with incident light from a lens by using a solid imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complimente Metal Oxide Semiconductor), and allow the image to be taken out after conversion into an electrical signal. Moreover, due to requirements for downsizing and higher performances of portable devices such as exchangeable lens type DSCs (Digital Still Cameras), fixed-lens type DSCs, and camcorders, the lens barrel as a main component part of an imaging apparatus is facing needs of further downsizing, weight reduction, and thinness. Generally speaking, a lens barrel is composed of a plurality of lens groups, such that each functional unit, e.g., a zooming function or a focusing function, corresponds to one group.
In such a lens barrel, a zoom lens group and a focusing lens group are provided so as to be capable of moving along the direction of an optical axis. For example, the zoom lens group is held in a lens holding frame. Furthermore, a guide shaft for guiding the lens holding frame along the optical axis direction is provided, the guide shaft being securely supported by the lens barrel. Furthermore, an actuator, e.g., a motor, for moving the lens holding frame is provided in the imaging apparatus. Light from a subject travels through the zoom lens group, whereby an optical image of the subject is converged onto an imaging device.
As a moving mechanism for the lens holding frame, a lead screw and a rack gear are used, for example. Specifically, a rack gear which is fixed to the lens holding frame is energized against a lead screw by a rack spring or the like. As a result, the rack gear meshes with the lead screw. Furthermore, by rotating the lead screw with a motor, the rack gear is moved. In synchronization with the move of the rack gear, the lens holding frame moves.
For example, in a lens barrel of Patent Document 1, two lead screws, respectively for a zoom lens holding frame and a focusing lens holding frame, are rotated by a single motor, and a rack gear meshing with each lead screw is separated from the lead screw with a predetermined timing to disengage meshing.
In a lens barrel of Patent Document 2, one lead screw and a switching plate are provided, and either one of the zoom lens holding frame and the focusing lens holding frame is selectively meshed with the lead screw, and moved along the optical axis direction.
Patent Document 3 discloses, with the purpose of stabilizing the behavior of a lens holding frame when moving along the axial direction, providing an energizing member in between a guide shaft and a lens holding member.
Citation List
Patent Literature
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2002-162555
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2009-69269
[Patent Document 3] Japanese Laid-Open Patent Publication No. 2007-232889